دانلود رایگان ترجمه مقاله عملکرد، کیفیت بستر و انتشار بوی گازی جوجه های گوشتی حاوی فیتاز (نشریه الزویر ۲۰۱۶)

عملکرد، کیفیت بستر و انتشار بوی گازی جوجه های گوشتی با تغذیه رژیم غذایی با مکمل فیتازی

Performance, litter quality and gaseous odour emissions of broilers fed phytase supplemented diets

Abstract

The effect of graded levels of phytase on performance, bone characteristics, excreta/litter quality and odorant emissions was examined using 720 Ross 308 male d-old broilers. A 2 × ۴ factorial arrangement of treatments was employed with 6 replicates of 15 birds per pen. Factors were: diets-positive and negative control (PC, NC); phytase – ۰, ۵۰۰, ۱,۰۰۰, ۱,۵۰۰ FTU/kg. The PC was formulated to meet the 2014 Ross 308 nutrient specifications, whereas the NC was formulated with lower Ca (−۱٫۴ g/kg), available P (−۱٫۵ g/kg), Na (−۰٫۳ g/kg), dLys (−۰٫۲ g/kg) and MEn (−۰٫۲۸ MJ/kg) equivalent to nutrient matrix values for 500 FTU/kg phytase in the starter, grower and finisher periods (i.e., downspec diet). On d 24, phytase decreased FCR by 1.6, 4.3 and 4.6 points at inclusion levels of 500, 1,000 and 1,500 FTU/kg, respectively (P < 0.01) across all diets. Phytase by diet interactions on BW gain were observed on d 24 and 35 (P < 0.01). The effect of phytase was much more pronounced in the NC diet as compared with the PC diet. On d 24, phytase increased BW gain by 37, 55 and 68 g in the PC and 127, 233 and 173 g in the NC at 500, 1,000 and 1,500 FTU/kg, respectively. Diet by phytase interactions were also observed for tibia ash, litter quality and water to feed intake ratio (P < 0.01) with higher phytase effect in NC as compared with PC. Neither diet nor phytase impacted excreta moisture content on d 18 or 21 (P > 0.05). Solid phase micro-extraction gas chromatography-mass spectrometry (SPME-GC-MS) analysis of gaseous emissions on d 39 indicated no difference in the emission of alcohols, aldehydes, ketones, volatile fatty acids and phenols between treatments (P > 0.05). The results indicate that phytase has greater benefits when formulated using nutrient matrix values as compared with adding it over the top in an already nutrient sufficient diet. The later method would be expected to increase feed costs without concomitant performance benefits.

۱ Introduction

Phytase is commonly used in broiler diets to degrade the phytate content, thus eliminating its anti-nutritional effects, which include reduced nutrient digestion, increased endogenous losses of nutrients and decreased performance (Woyengo and Nyachoti, 2013). The degradation of phytate at ileal or total tract level has been shown to be incomplete at the standard 500 FTU/kg inclusion rate of phytase (Selle and Ravindran, 2007). Phytase at higher levels produces extra-phosphoric effects in broilers, such as improved energy, amino acid and P digestibility (Amerah et al., 2014; Cowieson et al., 2011), and enhanced growth and feed efficiency (Walk et al., 2014). A recent study showed improvements in litter quality with higher doses of phytase (Bedford and Walk, 2015), although some reports suggest that phytase is associated with wet litter (Debicki-Garnier and Hruby, 2003; Bedford et al., 2012). Phytase may increase water consumption and contribute to wet droppings when formulated into diets without using nutrient matrix values. Phytase is normally assigned nutrient matrix values for amino acids/protein and energy in addition to Ca and P to incorporate it into least cost formulations (Shelton et al., 2004). The level of Na in basal diets and Na matrix for phytase are often overlooked during formulation. High dietary Na and/or Ca levels may trigger increased water consumption and hence diuresis and wet litter (Collett, 2012). Phytase added at higher rates without lowering dietary Na and/or Ca may consequently affect litter quality.

Wet litter and odour issues from poultry farms have become prominent worldwide. It is important to maintain litter quality to promote bird health and welfare and to minimize odour emissions. Litter quality may deteriorate due to increased excretion of minerals by birds (van der Hoeven-Hangoor et al., 2013). Phytate can bind with minerals and protein in the diet making them unavailable for digestion (Cowieson et al., 2006; Selle et al., 2012). Phytase may therefore potentially improve litter quality by increasing the bioavailability of minerals and protein. Excreta/litter quality is generally measured by water activity, moisture and free water contents (van der Hoeven-Hangoor et al., 2014). The amount of water in the litter has been found to affect microbial activity (Himathongkham et al., 1999; Wadud et al., 2012), ammonia emissions (Miles et al., 2011) and odorant emissions (Sharma et al., 2016). It is, therefore, important to study the effect of phytase on litter quality and odour emissions together with performance, especially when used at higher levels. The aim of this study was to investigate the effects of graded levels of phytase in nutritionally adequate and downspec wheat based broiler diets on performance, excreta/litter quality and odour emissions.